"Although these particles are ten million times smaller and rotate more than one million times faster than the rotary blades of a helicopter, we can not only make their movement visible, but even manipulate it by using laser light“, says first author Stefan Kuhn of the Faculty for Physics at the University of Vienna in a press release. Due to the asymmetrical form of the rods, the researchers from the University of Vienna, Tel Aviv University and the University of Duisburg-Essen observed up to three times stronger optical forces at work than one would expect for round particles featuring the same mass.
The nanoparticles were produced at the University of Tel Aviv. A “forest” of standing rods was etched from the surface of a silicon wafer, whose thickness is about 200 times thinner than a human hair. Separately produced predetermined breaking points were the basis for the rods to crack in a Viennese quantum laboratory thanks to laser pulses on the back side of the silicon wafers. The detached particles then fly in a vacuum device through an optimal resonator, which reinforces the infrared laser light to an output of several hundred watts.
The free-flying and rotating nanoparticles disperse part of the light depending on their position and orientation. This enables every movement of every single participle to be monitored in real time with a resolution of a millionth of a second. In addition, the light exerts force on the movement of the particles, in which case their speed and movement can be influenced.